There are more than twenty halls in front of cave in Mogao Grottoes,such as caves No.130,108,100,98,96,95,85,76,74,72,61,55,467,53,46,45,44,39,38,35,30-27,33-21,Most of caves have its own eaves building.The two kinds of architecture are both timber construction.After carefully research,we find that these special architecture were built during early Tang dynasty at the first time,developed in Middle Tang,and very popular during the period of Gui-Yi-Jun,and still continued in the West Xia and Yuan Dynasty.In this paper,the author specially discusses the two halls in front of caves No.130 and No.96.